This invention relates generally to an integrated circuit for a timepiece of the type used for driving the step motor of an analog display, and more particularly, to a circuit where the size of the transistors is substantially reduced. In a conventional electronic analog timepiece, since there is only one supply voltage, generally a battery, the transistors for driving a step motor are driven by the same voltage as is used for integrated timekeeping circuits. Also, in hybrid watches having both an analog display and a digital display, the step motor driving transistors again are driven by the same battery voltage as in the simpler, purely analog timepiece. For driving the step motor, a high level of current, several hundred microamperes, flows, although the peak current continues for only a short time period. To accommodate this high current requirement, the CMOS integrated circuit structure, that is, in particular the driving transistors, requires a large surface area. Accordingly, the cost of the integrated circuit chip is greatly influenced by the area of the driving transistors. It is desirable that the size of the integrated circuit chip be small as possible so as to decrease the cost of the chip and also raise its reliability. When the area for the step motor driving transistors is made smaller, the entire area of the integrated circuit chip for the timepiece can be made smaller. The same object of smaller size is equally applicable in the hybrid watch having both analog and digital displays.
What is needed is an integrated circuit for a timepiece which has a small area and yet provides the high current carrying capability required for operation of the step motor in the analog mode of operation.